利用固相碳源协同作用制备碳纳来管及其生长机理的研究

发布时间：2018-04-29 12:47

  本文选题：碳纳米管 + 固相碳源　； 参考：《北京化工大学》2015年硕士论文

【摘要】：碳纳米管作为一维炭材料的典型代表,因其独特的电磁、力学、热学、光学等性能,在纳米电子器件、复合材料、生物医疗、储氢材料等领域被广泛研究。经过多年的发展,在制备方法、生长机理以及应用领域等方面取得了巨大的成果,被誉为21世纪最有前途的材料之一,但目前还没有一种方法能够制备出结构规整、纯度高、层数可控的碳纳米管,因此在结合现有的制备方法的基础上,提出新的制备工艺是一种可行的途径。本文利用固相碳源与催化剂混合、炭化,并在助催化剂的作用下,合成多壁碳纳米管。采用SEM、TEM、HRTEM、XRD、Raman等分析表征手段研究碳管的形貌结构。结果发现用该方法制得的碳纳米管直径为50～100nm,长度为0.2～4μm,管壁较薄,直线型,结晶性能较好以及内部有较高催化剂填充率。在实验过程中,通过改变碳源的种类和颗粒大小、催化剂的类型及与碳源混合方式、酸化时间、反应温度、保温时间以及H2O和噻吩(C4H4S)添加量等参数,最终获得了碳管的最佳合成条件：选择利用10～20μm的天然石墨通过改性的H法氧化24h得到的氧化石墨烯为碳源,NiO/MgO为催化剂,按照质量比3：10的比例,在乙醇溶液中混合均匀并加热蒸干,在850℃炭化,保温6～10h,并同时通入1.5ppm·min-1的水蒸气和1ppm·min-1的噻吩,最终得到形貌较好的CNTs。通过对实验结果分析,提出一种新的制备CNTs的生长机理,其过程如下：(1)氧化处理使得碳源表面含有大量官能团和活性较高的碳位点,可以均匀吸附和锚合催化剂颗粒；(2)在炭化过程中,催化剂被还原,同时吸附S原子使其熔点降低,在Ostwald熟化作用下相互融并；(3)催化剂颗粒刻蚀碳层并吸附、溶解碳原子簇,使催化剂中碳的浓度升高；(4)当碳浓度增大到一定量时,在催化剂表面析出碳层,继续吸附S和刻蚀碳源,使得催化剂体内压力增大,在膨胀作用力下,催化剂变形拉长；(5)随着吸附S原子的饱和以及碳源的耗尽,生长结束,最后形成碳包覆金属硫化物的碳纳米管。本实验制得的CNTs作为锂离子二次电池负极材料具有较高的比容量和循环稳定性。在小电流密度50mA·g-1下,首次放电比容量达到957.3 mAh·g-1,循环50次后仍保持600mAh·g-1左右。通过前三次充放电电容量-电压曲线以及循环伏安曲线分析得出,填充在碳纳米管中的金属硫化物有较高比容量,在今后实验中,适量的保留填充在CNTs中的金属硫化物可以有效地提高材料的储锂性能。
[Abstract]:As a typical representative of one-dimensional carbon materials, carbon nanotubes (CNTs) have been widely studied in the fields of nano-electronic devices, composite materials, biomedical materials and hydrogen storage materials because of their unique electromagnetic, mechanical, thermal and optical properties. After years of development, great achievements have been made in preparation methods, growth mechanisms and application fields, which are regarded as one of the most promising materials in the 21st century. Because of the controllable layers of carbon nanotubes, it is feasible to propose a new preparation process based on the existing preparation methods. In this paper, multi-walled carbon nanotubes (MCNTs) were synthesized from solid carbon source and catalyst by carbonization and co-catalyst. The morphology and structure of carbon tubes were studied by means of Raman analysis and Raman analysis. The results show that the diameter and length of carbon nanotubes prepared by this method are 50 ~ 100 nm and 0.2 渭 m respectively. The tubes have thin wall, linear shape, good crystallinity and high filling rate of catalyst. During the experiment, by changing the kinds and particle size of carbon source, the type of catalyst and its mixing mode with carbon source, acidizing time, reaction temperature, holding time and adding amount of H _ 2O and thiophene C _ 4H _ 4S, etc. Finally, the optimum synthesis conditions of carbon tube were obtained: the graphene oxide obtained by oxidation of 10 ~ 20 渭 m natural graphite for 24 h by modified H method was used as the catalyst of nio / MgO, and the mass ratio of nio / MgO was 3:10. After mixed in ethanol solution and heated and evaporated, carbonized at 850 鈩，

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